The present invention relates to a rigid endoscope, comprising a jacket tube having an optical system and a first glass fiber bundle shining parallel to the image axis of the optical system, for illuminating an object to be examined, and a second optical illumination system also aimed at the object to be examined.
It is known in principle that a rigid optical system for endoscopy, hereinafter called a rigid endoscope, comprises an optical system used for imaging a light source for illuminating the object being examined. It is also known, for instance from European Patent No. 0 369 937 A1, that the light source is realized with a glass fiber bundle, or so-called optical wave guide, located parallel to the optical axis of the optical system. In the prior are, the light from an external light source is input into the glass fiber bundle at the proximal end (the side toward the user) via a further glass fiber bundle, the so-called optical fiber cable. Via the glass fiber bundle, the light is transmitted to the distal end of the endoscope (the side toward the object being examined). The light source thus shines from the direction of the observer onto the object.
However, such endoscopes have the disadvantage that surgical instruments located in front of the optical system of the endoscope during the operation generally cast no shadow on the organs being examined. This is because articles introduced between the observer and the object being observed, hereinafter called the image background, are known not to cast shadows on the image background, if the light exit axis of the light source and the optical image axis of the observer coincide. Because of the endoscopic two-dimensional image, the surgeon already lacks depth information about the three-dimensional space being examined, and thus the three-dimensional impression of the region of the operation is restricted. In the endoscopes mentioned, this three-dimensional impression is restricted still further by the unnatural lighting or the absence of the shadow.
In angled endoscopes, such as a laparoscope with a 30.degree. viewing direction, there is a slight asymmetry, because of constructional requirements, between the light exit axis of the light source and the optical image axis of the observer. However, this asymmetry is kept as slight as possible, so that the angle between the light exit axis of the light source and the optical image axis of the observer tends toward zero, and shadow formation, which would increase the plasticity of image reproduction, is negligibly slight.
From German Patent 29 42 982 C2, an endoscope is known in which two light sources are provided for illuminating the near and far region in front of the optical system of the endoscope. Both light sources are embodied in the form of optical wave guides, whose free ends crosswise to the longitudinal direction of the endoscope are disposed immediately next to the distal end of the optical system of the endoscope. The light exits of the first light source extends parallel to the image axis of the optical system of the endoscope and thus to the viewing direction of the observer. To exclude the influence of parallax in the illumination of the near region by the first light source, the light exit axis of the second light source is inclined relative to the image axis of the optical system of the endoscope; the light exit axis of the second light source and the image axis of the optical system of the endoscope intersect, in the viewing direction of the user, in front of the optical system of the endoscope. The far region in front of the optical system of the endoscope is illuminated by the first light source that shines parallel to the image axis of the optical system of the endoscope, and the near region in front of the optical system of the endoscope is illuminated by the second light source, which shines in inclined fashion relative to the image axis of the optical system of the endoscope. However, like the endoscopes already discussed above, this endoscope, because of the only slight spacing between the distal end of the optical system of the endoscope and the free ends of the first and second optical wave guides, has negligibly slight shadow formation.